Abstract:

The broad aim of our study was to understand shrimp communities and the relationship between dominant species by conducting ecological niche analyses. We collected data with respect to quantities, biomass and species identification on shrimps from the Jiushan Islands Marine Nature Reserve in November 2015 and again in February, May and August of 2016. Using indices such as the index of relative importance (IRI), niche breadth and niche overlap, we analyzed the ecological niche of dominant shrimp species. Finally, we compared niche breadth to understand the relative resource utilization capacity of different shrimp species in the community and also identify whether shrimp species are evenly distributed across the sampling sites/seasons. We used spatio-temporal niche breadth which is a comprehensive descriptor of resource utilization and the product of temporal and spatial niche breadth. In total, we captured 16 warm-temperate and warm-water species in the marine reserve, belonging to 8 families and 12 genera. Seven dominant shrimp species (IRI > 500) were identified, belonging to four families and five genera. Results showed that relative shrimp resources varied with season and further revealed that shrimp biomass in spring and autumn were higher compared to summer and winter. Spatio-temporal niche breadth of all dominant species (except Exopalaemon carinicauda) was higher than the other species. The spatio-temporal niche overlap value between Alpheus japonicus and Parapenaeopsis tenella was the highest, indicating that these two species had highly similar resources utilization. On the other hand, Exopalaemon annandalei and Parapenaeopsis hardwickii, were least similar in their resource utilization. The importance ranking results calculated using IRI and niche breadth were not identical: Palaemon gravieri had the highest spatio-temporal niche breadth value, yet Alpheus japonicus had the highest IRI value. We note however that the indices used cannot reflect biomass of the species.

Key words: Jiushan Islands Marine Nature Reserve, shrimp composition, niche breadth, niche overlap, index of relative importance (IRI)